1. Field of the Invention
This invention relates to particulate insolubilized enzyme composites comprising a solid support which can be used and reused as a catalyst to initiate or promote enzyme-catalyzed chemical reaction. More particularly, the invention concerns relatively inexpensive solid-supported insolubilized biochemical catalyst compositions capable of functioning for long periods and useable in continuous processes.
Enzymes are known to be highly active and selective catalysts for many applications involving aqueous solutions of substrate materials. The enzymes are water-soluble protein-like substances. Consequently, when employed in water-soluble form, the enzyme is lost, used up or destroyed to prevent contamination of the ultimate product.
Recently attempts have been made to prolong the activity of enzymes by rendering them insoluble and thus amenable to reuse and recovery by fixing the enzyme upon a water-insoluble support. In the technique of primary interest there is a direct chemical attachment by covalent chemical bonds of the enzyme to an organic polymeric matrix or a porous inorganic solid. Particulate insoluble enzymatically-active enzymes have been produced using solid siliceous support material such as porous glass by reacting the particulate solid siliceous support material with certain organosilanes, e.g., gamma-aminopropyltrimethoxy silane, and attaching an enzyme to the reacted organosilane with a crosslinking agent such as a dialdehyde exemplified by glutaraldehyde. Porous glass particles and nickel-coated screen or other nickel-coated solids are currently the most popular supports, the porous glass being especially preferred because of the high catalytic activity per unit weight of support. Porous glass is, however, very expensive and the cost of enzyme catalysts based upon such support material is prohibitive for many possible industrial applications. Furthermore, porous glass is friable. During catalyst preparation, use and reuse, especially under conditions of strong agitation or high flow rates, the supported catalyst particles are subjected to mechanical forces. When, as in the case of supports based upon porous glass, the particles lack mechanical strength, they tend to break down into fines which are too small to be useful in catalytic reactors because of excessive pressure drops. Breakdown has been reported to result in leaching of the enzyme when it occurs after fixation of enzyme to porous glass.
The widespread industrial usage of insolubilized particulate enzyme catalysts awaits the availability of reasonably low cost products having high catalytic activity and in the form of small granular particles which resist breakdown under dry and wet conditions.
2. Prior Art
The following patents suggest the use of various clays as possible supports for enzyme catalysts wherein the catalyst compositions are obtained by covalently binding enzymes to a silanized support through various crosslinking agents.
U.S. Pat. No. 3,519,538 - R. A. Messing et al - July 7, 1970
U.S. Pat. No. 3,669,841 - R. E. Miller - June 13, 1972